Discuss back pressure

Advertisements always appear on the right side of posts on the second floor, ruining the format of the posts.

ASME PTC-25 -1994 states the following: ASME PTC-25 -1994 states the following:: a) Superimposed Back pressure : the static pressure e * stinging at the outlet of a pressure relief device at the time the device is required to operate. It is the result of pressure in the discharge system coming from other source, and it may be either constant or variable. Additional back pressure: The static pressure that exists at the outlet of a safety valve just before it operates. It is caused by other pressure sources in the exhaust system, which is divided into two types: constant and variable. 1) Variable back pressure is the superimposed back pressure that will vary with time. Variable back pressure is the additional back pressure that changes with time. 2) Constant Back pressure is the superimposed back pressure which is constant with time. Constant back pressure is an additional back pressure that does not change with time. b) built -up back pressure : pressure e * sting at the outlet of a pressure relief device caused by the flow through that particular device into a discharge system. discharge back pressure: The pressure that develops at the valve outlet due to the flow of media through the safety valve into the discharge system. c) Back pressure: the static pressure e * stinging at the outlet of a pressure relief device due to pressure in the discharge system. back pressure: The static pressure present at the outlet of a safety valve due to the pressure in the discharge system. We can summarize the relationship among all types of backpressures as follows:: 1. Total backpressure = Built-up Backpressure + Superimposed Backpressure Total backpressure = discharge backpressure + additional backpressure 2. Superimposed Backpressure could be either CONSTANT or VARIABLE for eg if a relief device relieves to atmosphere then it is CONSTANT and if the relief device relieves into, say, a flare header in which several other relief devices are relieving, then the superimposed backpressure is VARIABLE. The additional back pressure may be constant or variable. For example, if a safety valve vents to atmosphere, its additional back pressure is constant ； If the safety valve is bleeding to the flare main pipe, and several other safety valves are also bleeding to the flare main pipe at this time, the additional back pressure of the safety valve is variable.

I give a set of data to explain why I raise this question. My safety valve discharges the main pipe of the flare (condition), and the back pressure between my own installation area and the flare boundary area is 0.18MPaa. (1) constant back pressure 0.18MPaa (2) superimposed back pressure 0.012MPaa (3) allowable back pressure 0.2038 MPag (4) built-up back pressure 0.1918 MPa As can be seen from the above: (3) = (4) + (2) (4) is a pressure difference, and (2) here is smaller than (1) if it refers to additional back pressure. Please experts explain. The superimposed back pressure here may be dynamic additional back pressure, right? Is built up back pressure generally expressed in terms of pressure difference, or is it just a pressure difference? Is the superimposed back pressure of API520, as mentioned on the third floor, an additional back pressure but including constant + back pressure affected by simultaneous tripping of other safety valves? Now the question is out. (1) + (2) here is what API520 calls additional back pressure. This post was last edited by safetyvalve on 2008-3-3 13:15 ]

Here, aside from back pressure, it seems to be a concept in physics, that is: Pressure fluctuations have concepts such as effective average, amplitude and arithmetic mean. I wonder if they can be compared? Experts please answer.